Process of preparing highly-concentrated nitric acid.



lEtTIN MOEST, 01E H fiCHST-ON-THE-MAIN, GERMANY, ASSIG-NDK BY MESNE 'ASSIGN- MENTS, T NITRUM IENGESELLSC "snee Lllfitlfihll. Itl'o Drawing.

To all whom it may concern;

Be it known that l, Ph. D, chemist, a citizen of the Empire of Germany, residing at Hiichst-on-the-Main,

Germany, have invented certain new and usefullmprovements in the Process of Preparing Highly-Concentrated Nitric Acid,

' of which the followingis a specification.

it is known that aqueous nitric acid dissolves nitrogen peroxid (or nitrogen tetroxid) in large proportions. The maximum solubility depends, besides on the temperature, chiefly on the concentration-oi the acid ,used and increases with the augmentation therewith i made the surprising observation that each of these homogeneous layers again consists of nitric acid and N0 (nitrogen peroxid) and that one of these layers-in most cases that of the lowest specific grav- .ity'-contains a more concentrated acid (under favorable conditions nitric acid of about 100 per cent.) and the other layer a more diluted acid than that first used. Thus -it is possible to separate nitric acid and water from aqueous nitric acid by introducing nitrogen peroxid.

The process described in my following specification for preparing highest concentrated nitric acid, is based on the abovementioned, hitherto u a .mO'WlIl, facts.

This process consistsin intimately mixingaqueousn1tr1c acid of such concentration as it is for instance obtained by the process descnbed in United States Patent No. 1,050,160, with an excess of liquid N 0 in leayinrg this mixture at rest in order to al- 0 low the formation of the two layers, then separating thellatter and eliminating the NQ from the layer containing the concen trated acid (at ordinary temperature the upper one) by the usual means, for instance by distillation, whereupon a highly concen trated acid remains. The vapors oi the Ni),

anain'used. e other layer, containingthe dilute acid and NU may-again be enriched in the known manner, for instance by treat- MARTIN Monsr,

'centration, for instance one of 95 l T, 0]? ZURICH,

am, a conno- Q'li' PREPARING- HIGHLlT-CQNCENTRATED NITRIC ACID.

Patented Apr. is, rare.

a licatio filed 111M113, leis. Serial 1%. 19,037.

ing it with oxygen, and it can be further concentrated according to the new process. This peculiar dissolving action of the nitrogen peroxid also permits the direct preparation of highly-concentrated nitric acid from water or aqueous nitric acid and nitrogen peroxid by treating with oxygen a reaction mixture composed according to the foregoing indications. In such a heterogeneous system the formation of the nitric acid takes place very rapidly in the section containing the more dilute acid-because the newly-formed acidis continuously re-separated by the liquid N0 until an equilibrium corresponding to the composition is obtained. So long as oxygen gas passes through the mixture, the layers are whirled together in the form of small drops; it is even advantageous to stir at the same time. lln order to avoid any losses of N 9,, it is advantageous to cool with a reflux apparatus. The process may also be operated under pressure. The layers become distinctly visible when the liquid is atrest and after the current of oxygen is interrupted; they may be sepa rated as above-indicated and the NU may be separately removed tromieach of the layers. Thus, there is obtained an acid cl nearly 100 per cent. strength from the upper layer and from the lower layeraccording to the proportions useda more or less dilute aci'd. in many cases these proportions maybe so elected from the beginning that the two layers when united yield, after the NO is removed, an acid of the'desired conper cent. strength. v

Example-ll: 15 parts byweight of nitric acid of 81 per cent. strength are mixed and shaken with 30 parts by weight of liquid Thus there are formed-two layers which areseparated and from; each of which the nitrogen peroxid is separately removed. In the upper layer there remains hit nitrogen peroxid and the mixture is then" lett at rest.

Mid

an acid of. 98-99 ,per cent'strength and in the lower layer oneof '75 percent.

Example llll: A mixture composed of 60 and oil tho. parts of nitrogen peroxid is treated, while stirring, with a strong current parts of nitric acid of j 5 "per cent. strength:

may be condensed in the usual way and m5 of oxygen in a vessel provided witha suitable reflux coolingnpparatus.

' centrated nitric acid, 1 in treating aqueous nitric acid wlth such an When the absorption of the oxygen becomes very slow the operation is interrupted. After having removed the No. 2, there remains from the two layers when united an acid of about 95 per cent. strength, the upper layer alone leaving an acid of nearly 100 per cent. strength and the lower layer alone one 0f'85-9O per cent. strength.

' Having now described my invention, what claim is 1. In a process of preparing highly-conthe step which consists excess of liquid nitrogen peroxid that layers are forme p v 2. The process 'of'pr'e'paring highly-concentrated nitric acid, which consists. intreating' aqueous nitric acid with such an excess of liquid nitrogen peroxid that layers are formed, then separating these layers and removing the nitrogen peroxid from one at least of said layers. v

3; In a process of preparing highly-concentrated nitric acid',-the steps which consist in treating aqueous nitric acid with'such an excess of liquid nitrogen peroxid that layers are formed, and introducing oxygen into this mixture. a

he process of preparing highly-concentrated nitric acid, which consists in treating aqueous nitric acid with such an excess of liquid nitrogen peroxid that layers are 1 MARTIN .MOEST.

my signature 'Witnessesz' JEAN GRUNu, CARL GRUND. 

